Robust Hydrate Adhesion Contributed by Absorbed Liquid: In-Situ Formed Hydrate Embedded in Microrough Metal

Hydrate blockage is the primary constraint on stable operation of hydrate-based facilities for gas storage, seawater desalination, gas transportation, etc. While completely halting hydrate formation in long-term operations is difficult, inhibiting hydrate adhesion to the pipe wall surface is a superior approach. It is widely accepted that the suspended liquid droplet is key to hydrate adhesion, whereas the contribution of adsorbed liquid phase (e.g., adsorbed droplets or film) is often overlooked. Herein, by using molecular dynamics simulations and micromechanic force equipment, the adsorbed liquid is found to exhibit a faster hydrate formation rate than suspended droplets, primarily due to its enhanced gas solubility and superior gas diffusivity. Once the hydrate nucleates from the adsorbed liquid, it becomes embedded within the microroughness of the pipe wall, thus significantly strengthening the hydrate-pipe adhesion force. Moreover, the embedded hydrate layer on the pipe wall can act as an anchor point, capturing suspended liquids to rapidly fuse with it, a process that ultimately triggers hydrate blockage. Overall, this study highlights the key roles of absorbed liquid at the pipe wall surface on hydrate formation/adhesion behavior, and it provides invaluable insights into the design and application of novel functional pipe wall materials that inhibit hydrate blockage.